An assessment of acid wash and bioleaching pre-treating options to remove mercury from coal

The United States Environmental Protection Agency is expected to begin regulating the release of vapor-phase mercury from coal-fired power plants in the year 2007. Chemical pre-treatment methods were investigated for mercury removal effectiveness from pulverized low-sulfur North Dakota lignite coal. More limited results were obtained for a pulverized high-sulfur Blacksville bituminous coal. A two-step acid wash treatment showed removal rates of 60-90%, compared to one-step treatments with concentrated HCl, which yielded removals of 30-38%. Removal effectiveness is similar for first step solvents of water, pH 5.0 acid, or pH 2.0 acid followed by concentrated HCl as the second step solvent, and is independent of first step incubation time. Neither of two bacterial strains, Thiobacillus ferrooxidans and T. thiooxidans, was found effective for mercury removal.     

Aerobic degradation of 2,4-dinitrotoluene by individual bacterial strains and defined mixed population in submerged cultures

The degradation efficiencies of isomeric mononitrotoluenes (2- and 4-NTs) and dinitrotoluenes (2,4-DNT and 2,6-DNT) by either individual bacterial strains (Bacillus cereus NDT4, Pseudomonas putida NDT1, Pseudomonas fluorescens NDT2, and Achromobacter sp. NDT3) or their mixture were compared in submerged batch cultivations. The mixed culture degraded 2,4-DNT nearly 50 times faster than any of the individual strains. The mixed culture also demonstrated significantly shorter lag periods in 2,4-DNT degradation, a lack of nitrite or organic intermediates accumulation in the liquid medium and the ability to degrade a broader spectrum of nitrotoluenes over a wider concentration range. The presence of both readily degradable 2-NT (or 4-NT) and poorly degradable 2,6-DNT in the medium negatively affected 2,4-DNT biodegradation. However, the mixed bacterial culture still effectively degraded 2,4-DNT with only slightly lower rates under these unfavorable conditions, thus showing potential for the remediation of 2,4-DNT contaminated sites.     

Image scale determination for optimal texture classification using coordinated clusters representation

The efficiency of texture image classification is certainly influenced by image scale when a feature space or a classification method is not scale invariant. An alternative approach to the scale-invariant techniques is proposed that first estimates an effective image scale and then uses it to adjust texture features to get the best possible texture image recognition and classification. We use the correlation distance between pixels as a measure of the scale of texture images. We study the performance of classification of texture images in the coordinated cluster representation (CCR) versus an image scale and the size of the scanning window used for the coordinated cluster transform. Given the number of classes to be classified in, we find that an optimal (up to 100%) classification efficiency in the CCR feature space is obtained by changing an image scale and/or the size of the scanning window in the coordinated cluster transform.     

A beta-1,4-galactosyltransferase from Helicobacter pylori is an efficient and versatile biocatalyst displaying a novel activity for thioglycoside synthesis

Helicobacter pylori is a highly persistent and common pathogen in humans. It is the causative agent of chronic gastritis and its further stages. HP0826 is the beta-1,4-galactosyltransferase involved in the biosynthesis of the LPS O-chain backbone of H. pylori. Though it was first cloned nearly a decade ago, there are surprisingly limited data about the characteristics of HP0826, especially given its prominent role in H. pylori pathogenicity. We here demonstrate that HP0826 is a highly efficient and promiscuous biocatalyst. We have exploited two novel enzymatic activities for the quantitative synthesis of the thiodisaccharide Gal-beta-S-1,4-GlcNAc-pNP as well as Gal-beta-1,4-Man-pNP. We further show that Neisseria meningitidis beta-1,4-galactosyltransferases LgtB can be used as an equally efficient catalyst in the latter reaction. Thiodisaccharides have been extensively used in structural biology but can also have therapeutic uses. The Gal-beta-1,4-Man linkage is found in the Leishmania species LPG backbone disaccharide repeats and cap, which have been associated with vector binding in Leishmaniasis.     

New path in the thermal cracking of triacylglycerols (canola and soybean oil)

Triacylglycerols (TGs) are naturally occurring oils abundant in many crops. A series of batch uncatalyzed thermal decomposition experiments were performed using canola and soybean oils to explore pathways of TG cracking. A detailed gas chromatographic protocol based on mass spectrometric identification and flame ionization quantification was applied to the organic liquid product generated upon cracking. Reaction conditions were identified that resulted in a novel organic liquid product (OLP) composition compared to previously reported work. Under these conditions (temperatures within a 420-440 °C range) a new route for TG thermolysis was discovered in which cracking reactions of original TG-bound fatty acids were nearly complete and led to the formation of 15-25 wt.% C₂-C₁₀ linear saturated monocarboxylic acids and ca. 30% linear alkanes. Less than 2 wt.% C₁₆-C₁₈ fatty acids which were originally present in the feedstocks as glycerol triesters were found in the OLP. These reactions appear to be kinetically controlled due to abundant hydrogen formation. This route provides a significant enrichment of low-MW compounds in the OLP (65-70 wt.% being <C₁₁) and thus may be considered as a new option for the production of replacement products for petroleum-based fuels and chemicals.     

Quantifying a similarity of classes of texture images

To quantify the concept of similarity between classes of images three measures and algorithms of calculation are proposed. The first measure is calculated through the frequency of misclassification of subimages sampled randomly from images. The second one is calculated through the cross membership of the mass center of a class in a feature space. The third measure is defined through the membership of subimages, using the distance between each subimage and the mass center of a class in a feature space. We study these measures, classifying images in the coordinated clusters representation (CCR) feature space with the minimum distance classifier. A database of images of Rosa Porri?o granite tiles, previously classified by three human experts, is used in the experiments. The calculated similarity between classes is in excellent accordance with the qualitative evaluation by the human experts.     

A two-step acid mercury removal process for pulverized coal

A correlation predicting the effectiveness of a two-step acid wash coal cleaning protocol using sequential leaching of mercury from the coal was developed and the effectiveness of the two-step wash procedure was then determined for two bituminous coals. Increasing the hydrochloric acid concentration and temperature in the USGS four stage sequential leaching protocol increased the amount of mercury leached during the HCl step. Using these revised conditions, sequential leaching was then shown to correspond to the mercury removals achieved in the two-step wash method. Mercury removal rates of 50-70% were realized for the bituminous coals by pre-treating the coal prior to a wash with hot concentrated HCl.     

Cleavage of Carboxylic Acid Moieties in Triacylglycerides During Non‐Catalytic Pyrolysis

Noncatalytic pyrolysis of triacylglyceride (TG) oils is an attractive option for production of renewable fuels and chemicals. This process produces 20–30 wt% of C₂–C₁₀ fatty acids due to the presence of carboxyl moieties in TG. To decipher this process’ mechanism, several compositionally distinct crop oil feedstocks with varied abundances of C₁₈ saturated and unsaturated TG carboxylic acid chains were pyrolyzed for short residence times in a laboratory‐scale continuous turbulent flow reactor. A comprehensive gas chromatographic analysis of the oxygenated products revealed the selective formation of linear saturated monocarboxylic acids (LSMCA) of less than C₁₁ in size, with a specific homological pattern featuring peaks for C₂–C₃, C₇ and C₉–C₁₀ LSMCA. The relative abundance of these size groups varied amongst the feedstocks cracked due to variations in the abundance of triunsaturated (linolenic), diunsaturated (linoleic) and monounsaturated (oleic) acids, respectively, in the original TG. We proposed a mechanism explaining the observed product speciation and homology profiles by the formation of acyloxyl biradicals as essential intermediates. High‐temperature C=C π‐bond hydrogenation with a concomitant σ‐bond cleavage yields C₉–C₁₀ LSMCA. This new path was confirmed by pyrolysis experiments with triolein in a GC pyroprobe.     

A Graphene‐Based Coaxial Fibrous Photofuel Cell Powered by Mine Gas

Flexible photofuel cells (PFCs) have triggered strong scientific interest as promising emerging energy conversion devices for clean power generation due to their potential advantages in low‐cost, simple fabrication, room‐temperature operation, and high conversion efficiency, etc. However, how to enable a PFC with excellent structural flexibility and robustness, and meanwhile with sufficient fuel fed onto electrodes and therefore high power generation remains a significant challenge. Herein, a high‐performance coaxial cable‐shaped PFC device is successfully designed and integrated by employing wet‐spun graphene fiber as the inner cathode, TiO₂ nanoparticle‐intercalated graphene spring as the outer photoanode, and a robust polymer gel coated in‐between as the electrolyte separator. The as‐fabricated fiber‐shaped PFC demonstrates effective adsorption of fuel, essential light penetration, and rapid electron/ion transport. Importantly, the fiber cells are sensitive to methane‐based mine gas under sunlight, exhibiting a photocurrent density nearly three orders of magnitude higher than that in air, and excellent and reliable photovoltaic performance with a maximum power density of 0.04 W cm^?2 at 0.35 V. This work has shed light not only in using cheap mine gas for efficient power generation, but also on new strategies for design and fabrication of high‐performance PFCs in flexible electronic devices.